Variable pitch propeller



Feb 21, 1950 c. 1. LATHREM VARIABLE PITCH PROPELLER 4 Sheets-Sheet 1 Filed Nov. 6, 1944 R T Y O A E TL N N R E] 0 Vs T m5 m L r m j C. l. LATHREM VARIABLE PITCH PROPELLER Feb. 21, 1950 4 Sheets-Sheet 2 Filed Nov. 6, 1944 lNVEN I'OR CHARLES I. LATHREM ATTORNEY Feb. 21, 1950 c. 1. LATHREM VARIABLE PITCH PROPELLER 4 Sheets-Sheet 3 Filed Nov. 6, 1944 INVENTOR CHARLES I. LATHREM Y ATTORNEY Feb. 21, 1950 c. l. LATHREM 2,498,109

VARIABLE PITCH PROPELLER Filed Nov. 6, 1944 4 Sheets-Sheet 4 l I: I" 122 w 5 1Z2 1'' W M "Z #4 I52 I29 I45 4/ [1% I53 INVENTOR CHARLES I. LATHRM ATTORNEY Patented Feb. 21, 1950 N l TED TATES PATENT OFFICE 2,498,109 v VARIABLE .PITCH PROPELLER Charles I. Lat-hrem, Quebec, Quebec, Canada, as

'tiontof-Canada Application November 6, 1944 Serial No. 562,083

This invention relatesto airplanepropellers and more particularly to that type sometimes "called changeable or variablepitchpropellers.

The invention "provides propellers which may be adjusted to operate at a "predetermined fine pitch or to operate at a predetermined course pitch by means o'f'operating mechanism which is self-contained in'the propeller hub.

According to one form ofdevice embodyin the inventiona hollow hub having radially extending hollow armstosupportthe root ends of thepro- ,peller blades for rotation, also serves as ,a reservoir for hydraulic'fiuid. :Afluid pump is mounted in the hub. By means of-this pump, WhiCh-Dperates in response torotationroi the propeller, thefluid caused to act upon an'hydraulic motor within the hub. This motor-has a pistonwslidabl-ealong a hub insert;theihubinsertserving also to mount .the propeller on the engine driveshaft. :By means of a valve within the 'hub, .but adjustable from without; the fluid-pressure from the .pump may. be routed to force the piston axially-in one direction or the other. TheaXial-movement of the piston is translated into'blade rotating torque'by means of lever mechanism connecting the piston and root ends of theblades. Suitable stops-are provided to retain theblades in predeterminedfine pitch position-When" the pistonis urged in the corresponding direction and to retainthe .blades inpre'determined .coursepitch,p'osition when .the piston. is urged in the opposite direction.

' Although the novel features which .are, b elieved .to be characteristic of .the invention will be particularly .pointed out in the claims appended hereto, the invention itself, as to its objects and advantages, and themanner in whichitmay be carried out, may be better understood by referring .to the following description taken in; connection 'withthe accompany n drawings. forming apart hereof, in which:

1 .Fig. .1 .is across-section of the propeller assembly mountedon the drive .shaftof an airplane 'engine on line l-,l of.Fig. :2

Fig. -2:is:a view ofxthea'propeller'on line 32-42 of Fig. 1;

Fig.5 is aview in sectionon line.=3.:3.0f: Fig.1;

Fig. 4 isa View on line.4-4;,of Fig. 1;

Fig. 5 is a plan view of the pump unitsin the hub tolargerscale;

. Fig. :6 is, aviewiin section ofUthepump on 'line .i5'-'-,6 of.-Fig.;7;

"Fig.3 is=a view insectionwof the pump on'wl-ine 1-4. :of- Fig. 16 and l'l-iClaims. (Cl. 170160.32)

. 2 "Fig. 8 is a-view in'horizontalsectiorrof the control valve.

The propeller shownin the drawings comprises, ingeneraL-a hub lll, propeller blades ,4 la and ahollow insert l2 serving to mount the-propeller on the engine drive-shaftl3. Thedrive shaft extends through a bracket I4 fixed to the airplane engine.

The hub, designated generally by reference character 10, has a hub barrel 1-5 of generally cylindrical'sh-ape from which extends hollow arms I6 and I6aradially from-the'hub barrel. 'Inasmuch as each-"charms l6--and l-6a-and the-blade similar-to those parts-having-the same reference character without sub-letters.

The root end of propeller blade ll ismounte in aferrule 11 having a cylindrical wall portion l8, and a base-portionJQthrough whichextend lag bolts 20 toi-s'ecure the blade-to the-ferrule.

Theferrule, 'and hence the blade l l,is mounted 'for rotation about the blade axis' 2 I.

The ferrule-i l is-moun-ted in bearings 22 and 23 of radial thrust type, each 'comprising balls mounted in an i inner ringrace "25 and an outer ring race 26. The inner' bearing 23 rests upon an a split ring 52 -On'the ferrule 11. An annular flange 21 on the ferrule ll maintains the bearings 22 and '23 in spaced 'relation-and serves-to take the thrust when the propeller is rotated-about its axis of rotationifi. iA threaded blade retention nut I 29 maintains the hearings in place. 1 'A pack ing ring30 serves to prevent hydraulicfluid; later to be described, from leaking out *of *the hub. A nut retention plate I having radially extend ing projections registering with slots 32 in the hub arm is securedto hub retention nut 29 *by screws 33. The hollow hub insert l 2 is mounted in the hub and secured thereto' in suitable manner, as -*by welding. It is in general of cylindrical shape and has a'bore 4| which may 'be'tapered. slightly from the rear (that is, the end nearest the engine) toward the front-end. -Its interior surface has splines 34 and grooves "35 which register with corresponding splines-and grooves'on the exterior surface of'the drive shaft. '-The'drive;shaft l=3*has abore 36."

The inner end of'hub insert |-2-' is flared and-the I flared portion 31 has a tapered interior surface38. The outer end of the "insert also has a fiared portion 39 having a' tapered interior surface 10 tapering inwardly toward the rear. When the propeller is mounted on the engine drive shaft l3 a spacer ring 42 abuts the shaft nut 9. A rear cone ring 43 abuts the spacer 42, and the interior surface 38 of the insert flared portion 37 engages the exterior tapered surface 44 of the cone ring 43. A split front cone ring 45 fitting around the forward end of the drive shaft 13 has a tapered surface 45 engaging the interior tapered surface 40 of the insert flared portion 39. This split cone ring 45 has an outwardly extending cylindrical wall portion 41 having an annular groove 48.

To secure the propeller to the drive shaft l3 there is provided an internally threaded shaft nut 49, the threads of which engage corresponding external threads on the shaft. An annular flange 50 on the nut 49 fits into groove 48. Hence, when the nut 49 is tightened and adjusted the propeller is made fast to the engine shaft. When the propeller is thus made fast to the shaft, a shaft nut pin 53 extending through registering apertures in the shaft nut and engine shaft prevent the nut from turning on the shaft, thus to maintain the propeller properly secured to the engine drive shaft, notwithstanding vibrational or other forces which may tend to rotate the nuton the shaft.

The exterior cylindrical surface of the hub insert I2 is provided with spaced annular flanges or bosses 60 and 6|, the boss 60 for convenience of description being designated as the front boss, and boss 6i, as the rear boss. At their outer peripheries these annular bosseshave machined or smooth surfaces 62 and 63. Each boss on the inside is hollowed out to provide in effect annular spaces 54 and 65. The peripheral exterior surface 66 of the insert between the spaced bosses B and 6! is also machined or smooth. A split ring piston, designated generally by reference character 57, comprises two complementary half sections each of similar construction. When assembled on the insert, the piston may be said to comprise an annular piston which is an inwardly extending portion 68 within a sleeve 69. The annular or ring piston 68 engages the exterior surface 66 of the insert and the sleeve portion 69 of piston 61 has an interior surface 10 which is machined or smooth and engages the peripheral surfacesBZ and 63 of the annular bosses B0 and GI. The piston 61 is slidable coaxially along the insert l2.

For convenience of assembly, the piston is made up of two complementary half sections H and Ha (see Fig. 2). Since both are similar in construction only one is described. Half section H has a lug 72 having a bore 13 which is internally threaded and has, on the opposite side, a lug 14 having an internal bore 15. Half section Ha is similar and has corresponding but complementary bosses and bores. When fitted to gether in complementary fashion around the insert with the sleeve 69 of the piston 61 engaging the outer surfaces of the annular bosses 6B and BI the bore 13 registers with bore 15a and bore 15 with bore 13a. Pins 16 and 16a each having a threaded end, a nut portion and also a projecting slot-engaging portion, secure the two half sections H and Ha together. As shown in Fig. 2 pin 76 is externally threaded at one end to engage the threads of lug 13a. An integral nut 11 provides a convenient means to tighten the pin. The outer end of the pin has a, slot-engaging portion 78 disposed within the slot 19 of lever 80, described in further detail hereinafter. Pin 16a, is of similar construction and corresponding parts are desig- 4 nated by the same reference characters with the sub-letter a.

The annular piston portion 68, which may be referred to for convenience of description as a ring piston, comprising the two half sections, is provided with an annular groove 8| to accommodate a packing ring 82. The packing ring may be held snugly against the cylindrical surface 66 by means of a helical spring 83 within the groove and extending around the packing ring.

Boss 60 is provided with a port 84 connecting with the interior annular space 64 and boss BI is provided with a port 86 connecting with the interior of annular space 65. As described in further detail hereinafter, hydraulic fluid under pressure may be routed through the ports 84 and 86 to move the ring piston 68, coaxially in either direction between the bosses 60 and 61 From the foregoing description it will be seen that the piston sleeve 69 with ring piston 68 together with exterior surface 66 of. the insert and the annular bosses 60 and 6| provide a double acting hydraulic motor adapted to operate the piston 61 in either direction. The motor may be operated by hydraulic pressure as described hereinafter.

As mentioned above, pin projection 18 engages a slot 19 in lever and pin projectionlBa engages a corresponding slot 19a in lever 99a. Lever 89 comprises an arm 81 which engages base 19 of the ferrule l1 and is securely attached thereto near the periphery of the ferrule base by means of lag bolts 88 dowels 99 serving to align the lever with the ferrule. Fixed to the arm 8! is an angle arm 9| having in its outwardly extending portion, a slot 19 whichaccommodates the pin projection 18. With more particular reference to Figs. 2 and 3, it will be observed that when the piston 51 is moved coaxially along the insert, the pin projection also moves coaxially. Its movement is translated to the lever since the pin engages it in the slot 19. However, the other arm 81 of the lever 80, being fixed to the base of the ferrule, the coaxial movement of the piston 61 is translated to rotary motion through the lever. Thus a torque is exerted to rotate the ferrule l1, and hence the propeller blade I I, about its longitudinal axis. Blade Ha. is, also rotatable about its longitudinal axis in similar fashion by the lever 80a.

A stop arrangement is provided to control the adjustment of the propeller blades within predetermined limits for fine or course pitch position. This arrangement comprises a split clamp ring 92 and a lug secured to the periphery of the hollow arm it of the hub. A similar arrangement is provided for each propeller blade.

A typical-clamp ring comprises two half sections 96 0f similar construction. The outwardly extending lugs 93 and 94 having registering apertures accommodating a bolt 97. Corresponding lugs and bolts on the opposite side-from that as viewed in Fig. 2 are provided. Consequently, provision is made by bolts on both sides of the ferrule whereby the distance between the stops 93 and 94 may be adjusted, and the-ring may be clamped securely to the ferrule. It will be observed, also, that the spaced stops may be positioned where desired about the periphery of the ferrule. v e

Thus, when the stops are properly adjusted, the stop 93 will engage lug 95 when the piston 61 is urged to its rearward position on the insert, and stop 93a will engage lug- 950;. In this position the propeller blades are adjusted, for fine pitch.

.Eigs. 5 to '7).

'means of screws I08.

".5 n the other hand, when the apiston F6] is urged .toits forward position the propeller blades are ;rotated in the opposite directionabout their longiplace stops on the insert to cooperate with'the piston of the hydraulicrmotor for the purpose of limiting pitch adjustment.

To actuate the piston 61 there is provided :8. .suitable pump which is preferably of rotary type mounted within the hub. As shown inthe drawings, the pump I00 is ofthe rotaryvanetypelsee It comprises two blocks ,I-0-I and .102, one of which containsintake .port I03, discharge port I04, and pressure adjusting mechanisms I and the other,.clamped by screws I I5 to the first, providing a chamber I06 to accommodate the rotor M1. The pump I00 .is shaped .to be mounted within the hub without interfering with the operation of the piston 61. .It ma be @secured to the interior surface of the hub by The rotor I0! is mounted eccentrically to be rotated in the rotor chamber I06. It may have radially disposed slidable vanes I09. .As stated before, thehub chamber .85, provides a reservoir for hydraulic fluid; oil having been found preferable for the desired purpose.

-When the rotor shaft .I I0 is rotated inproper direction the'pump takes suction through port 1103 from the reservoir provided by hub chamber .815. The oil travels through intake conduit I I I, then through the rotor chamber I06, and is discharged under pressure through discharge conduit H2 and then through discharge port I04. It will be observed that block IOI is provided with grooves H3 and I I4 at the intake and outlet ports of the chamber I06. The pump discharge port .104 is connected by conduit I I15b to a routing valve II6 (see Fig. .3) described in further detail hereinafter. To prevent building up of excess pressure on the discharge side'of thepump, -:a .relief valve H8 is provided in the block I01. It will be apparent that by suitable selection and adjustment of spring l I 9, pressure in conduit II2 above a predetermined amount will move the vvalve :plug I I-8 out fromitsseat and relieve the .fluidpressure through relief vent .I2 I. The valve -plug I I 8 is yieldably held .in its-seatby the spring =.I I9 which in turn is held .by a cap I22, ,kept in :placeb asplit ring I23. .Thusmea-ns are provided, when-the pump is operating, to maintain -:a substantially constant fluidpressure on the discharge side of the pump and in the conduit II5.b leading to the fluid pressure routing valve H6.

The pump .is operated by means .of a;drive shaft -.Ii50 connected to the rotor shaft I I0 by a coupling I'5I, Drive shaft I50 extends through a housing -.Ir'52 which extends outwardly through the hub barrel wall. The housingmay be secured in suit- :ablemanner, as by welding. This housing I52 mounts .the pump drive shaft I50 for rotation in suitable bearings I53 and I54. Suitable packing I55 is provided to prevent leaking of oil from -the hub. Fixed to the outer end-of the pump drive shaft I50 is a gear I56 which meshes with 2. .fixed gear I5-I which in turn is secured 'to a anon-rotatable hubsleeve I58 attached to a plate .159 securely fastened to th bracket I4, as by means of bolts I60. Thus, rotatable gear I56 and :fixed gear I5! provide a sun and planet g ar arrangement. Accordingly, when thepropeller "isil'otatfid, .gear I56 fixed to pump drive shaft 1150 :revolves around the .sun gear 15143111113150 I6 :rotates "upon its :own axis to :rotate .pump a shaft 150 hence, .to' drive pump I I00.

The routing valve I I 6iprovidesmeans whereby :the fiuld:pressure: from'pump I00 "maybe routed either to conduit 125, which connects valve II'6 withportfifiin'bossrfiI and hence annular .cylindrical space 65, .orthe fluid pressure may .:be routed :to conduit -rI26 which connects the valve :with:port;84iin boss 6.0 and hence to the annular ;;cy1indrical-:spacez64 .onthe opposite side of :annularpiston 68. v

:Valve "l'Ifixcomprises a cylindrical body portion within which :is slidably mounted a pair of spaced pistons I28 and I29 mounted on stem -';I.33; piston I218 cooperates with :valve ports I30 and I3l. Port I30 connects with conduit lI5b.from :thepump, and valve port ;I'3.I connects with conduit I25 which .is .connected, as mentioned, :to :the double acting hydraulic motor. Piston I129 cooperates 'with port 130 and valve port 132, the latter port 132 connects with conduit I25 which is connected, as mentioned, to the other side-of the double acting hydraulic motor. Pistons I28 and I29 'areifixed tothe stem. I33, :whichextends "through a housing I34. The housing may be secured to the hub barrel in suitable manner, .as :by welding. The body of the valve is mounted within "the "hub barrel. The stem housing I34 extends from the rear of the hub toward the engine and s-issprovided with an annular shoulder I35 providing an abutment for helical spring ..I 36 which normally urges the'valve stem I33 outwardly from :t-hehub (that is, .toward the engine) to provide communication between ports I30 and I32. When in thiszposition port I3I'is vented through :the open end I;3'I of the-valvebody. The spring I36 also abuts'aring I238, slidable on the housing. The ring I38 is connected to the valve stem .133 by a pin I39 extending through the stem and :suitable slots I40 in the housing I34. A packing ring 'I4I provides a seal to prevent fluid leaking from thelhub tothe outside. The outer end oftthe valve stem is provided with a cap member I42. When thevalve stemis urged inwardly (that is, away from-the. engine) against the force of the compression 'spring .136, .port I30 communicates with'valve 'port I3I and port I32 communicates with ventport 'I 43.

To move the valve stem inwardly, there is provided 'a ring I6I, having a contact face I62, mounted 'on hub sleeve I58 "for axial movement. The bore of ring IBI is provided with "helical grooves I63, of which there are three equally spaced .circumf-erentially. Keys I64, of which :thererare three equally spaced circumferentially about the rhub'sleeve I58, register with the ire- .spectivegrooves. Consequently, upon rotation of ring I6I on the hub sleeve I58, the ring -I;6I is $10311S8d120 move axiallyonthe hub. A cord'I65 in an external groove IfiSrand fastened by a bolt "I 63I,.may "be used to rotatethe ring 'IGI from 'a "remote place; as, for example, from the cockpit .zof'the airplane. When the ring I;6I .is-rotate'd in proper direction itmay be caused to move axially toward thepropeller hub and 'thecontact face I62 will then engage the capmember M2 on the stem :of routing'valve I I6,-thus to cause pistons I28 and --I2-9 .to move inwardly (away :from :the engine) against "the .force of spring I36. When the ring 'I'6I is rotated in :the opposite direction it will be retracted axially along :hub sleeve 1:58, permit- .ztingthea-springzIBB 1130 move thexpistons outwardly (toward the engine) .to-rearposition. The ring :may beimoved towardthe engine :sufllciently to iuisengagesthe contact face I62iof ring :IiB'I :from

cap member I42 and then the pistons :28 and I29 take their normal rearward position under the tension of spring I36. To charge hydraulic fluid to the hub chamber 85, charging ports I68, closed by removable screws I69, are provided.

The operation of the device described in the foregoing is as follows: It may be assumed that the propeller assembly has been mounted on the engine as shown in the drawings. It may also be assumed that the hub barrel chamber is charged with a suitable oil of lubricating character. Also, it will have been observed that the parts have been sealed with packing material where needed and the parts otherwise joined in such fashion as to prevent oil from leaking from the propeller hub.

The propeller blades II and Ma are adjusted to the desired fine pitch position and the clamping rings 92 and 92a are clamped to the ferrules in such manner that at fine pitch position stop 93 engages lug 95 and stop. 93a engages lug 95a. When in this position levers 80 and 89a are in such position that the piston 61 will be in its rearward position. When the piston levers and stops are in this position the propeller is adjusted for fine pitch position. At the same time routing valve H is adjusted so that when ring IISI is in its forward position the valve stem I33 is in its forward position. Assuming that the propeller is rotating with the engine drive shaft, planet 1 gear I56 is rotating about its axis, while it revolves around sun gear I51, to operate pump I09. The operation of the pump sets up fluid pressure in conduit 51). By reason of pistons I28 and I29 of valve IIG being in their forward position, '4

the fluid pressure is routed through conduit I26 to exert fluid pressure on ring piston 68 to maintain the piston in its rearward position which corresponds to the fine pitch adjustment of the propeller blades. Fluid pressure on the opposite side of ring piston 68,that is, in annular chamber 65 is vented through conduit I back through the routing valve through port I32 and vent I43.

If it is desired to adjust the propeller blades to course pitch position, contact ring I6I is rotated in proper direction to cause it to be retracted axially toward the engine out of engage ment with cap member I42 on the stem of valve II6. This permits spring I36 to move the valve stem I33 and thus pistons I28 and I29 to their rearward position. When the valve is in this position fluid pressure in conduit II5b from pump I09, which is in constant operation when the propeller is rotating, is then routed to conduit I25.

This causes the fluid pressure to be exerted in annular chamber 65 of the hydraulic motor against ring piston 68, which drives the piston 61 to its forward position. Fluid pressure in chamber 64 of the hydraulic motor is then vented through conduit I26 through valve ports ISI and open end I37 of the valve body. When piston 61 is thus urged to its forward position, levers 8B and 89a rotate their respective ferrules I? and Ila until stops 94 and 94a engage their respective lugs 95 and 95a. In this position the blades are in their course pitch position. It will be understood, of course, that the stops 94 and 94a of clamps 92 and 92a will have been adjusted to correspond with the predetermined course pitch. It will also be observed that the distance between stops 93 and 94 and between 93a and 94a may be adjusted as desired for the limits of fine pitch and course pitch positions.

If it is desired to change the propeller from course to fine pitch, it will be apparent from the foregoing description that all that is necessary'is to rotate ring IEI to move it axially and forwardly from the engine. This again causes the contact face I62 of ring I6I to contact the cap member I42 which urges the valve stem I33 to forward position. When the valve stem is in its forward position fluid pressure is rout-ed through valve I I6 through conduit I25 to move the piston Glto its rearward position which corresponds to fine pitch position of the propeller blades, as described.

- From the foregoing it will be seen that the invention provides a controllable pitch propeller which is readily adjustable for operation in two positions, namely, fine or course pitch. The operating mechanism, comprising fluid pump,

control valve, conduits, and hydraulic motor, as well as the hydraulic fluid are all Within the 'and described with particular reference to the embodiment shown in the drawings it will be understood that various changes, substitutions, modifications or omissions of parts may be made by those skilled in the art Without departing from the invention comprehended by the following claims.

What is claimed is:

'1. For an aircraft propeller having variable pitch blades an hydraulic motor mountable within the propeller hub to rotate said blades about their axes, which motor comprises an insert having a bore adapted to drivingly connect the propeller to an aircraft engine crankshaft, spaced annular bosses having smooth peripheral surfaces, said bosses being secured to and extending around and outwardly from the exterior surface of said insert and serving with the exterior surface of said insert to provide an annular cylindri- "cal space to accommodate an annular piston, an

annular ring piston mounted on said insert and slidable axially along said insert between said bosses and having a sleeve slidable with said piston shaped to enclose the annular space between said bosses, the inner surface of said sleeve engaging the outer peripheral surfaces of said bosses and slidable thereon and the inner surface of said ring and piston engaging said insert ports leading into the chamber defined by said piston sleeve, bosses and insert through which hydraulic fluid may be forced under pressure to actuate said piston and means on said piston for connections to translate axial movement of the piston into torque to rotate said blades to change their pitch.

2. In an airplane propeller having variable pitch propeller blades, a hub having arms for mounting the roots of the variable pitch propeller blades, an insert of generally cylindrical shape having a hollow interior adapted to drivingly connect the propeller to an engine drive shaft, spaced annular bosses extending around the exterior surface of said insert and serving with the exterior surface of said insert to provide an annular cylindrical space to accommodate an annular piston, each of said bosses being securedto the insert at its inner edge and having a smooth surface at its outer exposed'peripheral edge, an annular piston mounted on said insert and slidable axially along'said insertbetween said bosses and shaped'to enclosethe annular space between saidbosses, said piston comprisinga: sleeve portion and a piston ringportion extending inward- 1y from the sleeve portion, the" inner surface of saidpiston ring portion engaging the exterior surface of said insert between the bosses and the inner surface of said sleeve portion being smooth and engagingthe outer-peripheral smooth surfaces of said bosses, means to exert fluid pressure'on said piston to cause said piston to move in a coaxial direction, and means connecting with said piston and the roots of said blades causing change of pitch of said blades in response to movement of said piston.

3. A variable pitch-propeller assembly which comprises a hollow hub having radially extending hollow arms, means for mounting a propeller blade in each ofsaidarmsfor rotation about its longitudinal axis to provide for" change of the pitchof such blades when-mounted in said arms,- a hollow insert mounted in" said hub having a bore to receivexthe drive shaft of an engine, spaced annular bosses around the exterior of saidinsert, an hydrauliclmotor includingan annular. piston in contactwith the exterior surface of said insertslidable coaxially back andforth between said bosses, a rotary pump within said hub, said hollow hub providing a reservoir for fluid to be circulated by said pump, means for causing said pump to operate when said hub is rotated about the axis of said bore, thereby to cause said pump to exert fluid pressure on said piston, a valve connected by conduits to said pump and motor having adjustable means to cause the fluid pressure from said pump to operate said piston coaxially in one direction or the other, means within said hub adapted to connect said piston and blades when mounted in said arms to change the pitch of such blades in response to movement of said piston, and a member adapted to be mounted independently of said hub and movable coaxially in the direction of the axis of said bore to make contact with said valve adjusting means, said valve adjusting means being operative to cause the said fluid to move said piston in one direction when said adjusting means is in operative contact with said member and in the opposite direction when not in contact with said member.

4. A variable pitch propeller assembly which comprises a hollow hub having radially extending hollow arms; means for mounting a propeller blade in each of said arms for rotation of the blade about its longitudinal axis to provide for change of the pitch of said blades; a hollow insert mounted in said hub to receive the drive shaft of an engine; an hydraulic motor within said hub; a fluid rotary pump within said hub having a shaft extending to the outside of said hub, said hollow hub providing a reservoir for fluid to be circulated by said pump; means including a stationary gear and a rotating gear meshing therewith on the outside of said hub causing said pump to operate when said hub is rotated by the engine shaft, thereby to cause said pump to exert fluid pres sure on said motor; a valve within said hub connected by conduits within said hub to said pump and to said motor, said valve having adjustable means to cause the fluid pressure from said pump to operate said motor in one direction or the other, said valve having a stem extending to 10 the outside of said hub; means including levers Withinsaid hub for connecting said motor and blades to change the pitch of said blades in response to operation of said motor; and a contact member-adapted to be mounted'independently of said hub and movable coaxially along said drive: shaft to make and break contact with said" valve stem to move said'valve adjusting means said valve adjusting means being movable to causethe said fiuid'to operate said motor in one blades, ahub. having; two. radially extending arms each for mounting the rootend of one ofi said blades for rotation; about its long axis, said; hub. serving as a reservoir for hydraulic fluid,.,a'n. insert mounted in said hub; said insert being of generally cylindrical shape and havinga hollow interior adapted to drivingly connect the propeller to an engine drive shaft,,a pair of spaced,

annular bosses, extending: around, the exterior surface of said insert and serving with the exeterior surface of said insert to provide an annular cylindrical space, tov accommodate. anlannular piston, each boss being secured at itsinner. edge to said insert and extending outwardly therefrom and having a smooth peripheral surface,

at its outer exposed edge,,.an annular piston con-,

structed of two half complementary, sections, mounted on said insertandslidable. axially along, said insert, said piston comprising a sleeve and a piston ring portion extending inwardly from the interior surface of the sleeve and engaging the exterior surface of said insert between said bosses, said sleeve being shaped to enclose the annular space between said bosses and having a smooth interior surface at each end, the interior surface at one end engaging the exterior smooth surface of one of said bosses and at the other end engaging the exterior smooth surface of the other of said bosses, means to exert fluid pressure on either side of said piston to cause said piston to move coaxially along said insert in one direction or the other, a lever mounted on each of said blades, a pin on each of said half sections, one pin connecting with one of said levers and the other pin connecting with the other of said levers, each of said levers producing a torque to rotate its connected blade upon axial movement of said piston.

6. A variable pitch propeller assembly which comprises a hollow hub having radially extending to hollow arms, means for mounting a propeller blade in each of said arms for rotation about its longitudinal axis to provide for change of the pitch of such blades when mounted in said arms, a hollow insert mounted in said hub having a bore to receive the drive shaft of an engine, an hydraulic motor within said hub, a fluid pump within said hub, said hollow hub providing a reservoir for fluid to be circulated by said pump, means for causing said pump to operate when said hub is rotated by such engine shaft when mounted in said bore, thereby to cause said pump to exert fluid pressure on said motor, a valve connected by conduits to said pump and motor having adjustable means to cause the fluid pressure from said pump to operate said motor in one direction or the other, means within said hub for connecting said motor and blades when mounted in said arms tochange the pitch of said blades in responseto operation of said motor, a hub sleeve adapted to be mounted independently of said propeller hub, a rotatable contact ring adapted to be mounted on said hub sleeve and movable coaxially along said'sleeve to make contact with said valve adjusting means, said valve adjusting means being movable to cause the said fluid to operate said motor in one direction when said adjusting means is in operative contact with said ring and in the opposite direction when not in contact with said ring.

7. A hub assembly for a variable pitch propeller for airplanes which comprises a hollow hub providing a reservoir for hydraulic fluid and hav ing radially extending arms, each arm being adapted to support a propeller blade for angular displacement about its longitudinal axis, whereby the pitch of blades mounted in said arms may be changed, a rotary pump mounted within said hub for pumping hydraulic fluid contained in said reservoir, a pitch adjusting hydraulic motor within said hub operative in response to fluid pressure exerted by said pump, pitch adjusting levers within said hub connecting said motor and blades and operated by said motor to angularly displace said blades and adjust the pitch thereof, a hollow insert mounted in said hub to receive the drive shaft of an engine for driving connection thereto, means including a planet gear connected to the driving'shaft of said rotary pump and a sun gear mounted independently of said hub to drive said pump in response to rotation of said hub, a valve mounted on said hub, conduit connections between said valve and pump and between said valve and motor, fluid flow 12 adjusting means in said valve adjustable to cause fluid from said pump to operate said motor in one direction or the other and a member mounted independently of said hub operable manually to adjust the direction of fluid flow by "make and break contact between said fluid flow adjusting means and member; said rotary pump, motor, pitch adjusting levers and fluid all being self-contained within the interior of said hub.

CHARLES I. LATHREM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

